Conversation with my brother Mike

My brother Mike is a retired mechanical engineer. I lasted nine months as an engineering student in college, but he graduated as an engineer and made a career out of it. A pretty extraordinary feat considering he never used an SI unit in his calculations.

I emailed him two pictures of duck and geese pelotons with birds drafting behind one another and the following (edited) exchange ensued:

Mike: Drafting in a more viscous fluid.  What would Osborne Reynolds say?

Me: He’s dead. Got a Ouija board?

Mike: I think having ones own dimensionless number confers immortality.

Me:  The Reynolds numbers for 3-, 7-, and 14-day-old ducklings . . . were 2.15 x 10^4, 2.82 x 10^4 [and] 3.60 x 10^4 . . .

I couldn't find a comparable set of measurements for Canadian goslings, but I have to believe they're the same order of magnitude.

 

https://www.wcupa.edu/sciences-mathematics/biology/fFish/documents/1995JEZ-DuckFormation.pdf


This is the money graf:

"The results of this study indicate that the least energetic effort is expended by the most posterior duckling in formation. Compared to a solitary duckling, trailing ducklings had values of AZ that were 3.4- 20.0% lower than leading ducklings with and without the decoy's wake. This finding suggests that the trailing duckling swims in a flow field different from the more anterior ducklings."

So even at high Reynolds number, drafting makes a difference. Not sure the same would be true for the E. coli swimming nearby.

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